Workup of a cyclododecanone cyclododecanol mixture in a sequence of side draw columns

Abstract

A process for removing a cyclododecanone-rich target fraction (A) from a dehydrogenation mixture (O) comprising low boilers (LB), cyclododecanone (CDON), medium boilers (MB), cyclododecanol (CDOL) and high boilers (HB) is provided. According to the process, substantially pure CDON is obtained via a distillative sequence of two side draw columns connected in series, wherein the sidestream of the primary side draw column is fed into the secondary side draw column. From the top of each of the two side draw columns, a CDON-rich fraction is drawn off, and these are combined to form a target fraction, which is essentially pure CDON.

The invention claimed is: 
     
       1. A process for removing a cyclododecanone-rich fraction (A) from a dehydrogenation mixture (O), the dehydrogenation mixture (O) comprising: components having a boiling point less than cyclododecanone (CDON) (LB); cyclododecanone (CDON);
 components having a boiling point between CDON and cyclododecanol (CDOL) (MB); 
 cyclododecanol (CDOL); and 
 components having a boiling point above CDOL (HB); 
 the process comprising: 
 a) feeding the dehydrogenation mixture (O) to a preliminary separator column; 
 b) distillatively removing the LB components from the dehydrogenation mixture (O) to obtain a first mixture (ABC 1 ) comprising the cyclododecanone (CDON), the MB components, the cyclododecanol (CDOL) and the HB components; 
 c) feeding the first mixture (ABC 1 ) into a primary side draw column ( 7 ); 
 d) drawing off a first cyclododecanone-rich fraction (A 1 ) from the top of the primary side draw column ( 7 ); 
 e) drawing off a first fraction (C 1 ) comprising cyclododecanol (CDOL) and the HB components from the bottom of the primary side draw column ( 7 ); 
 f) drawing off a second mixture (ABC 2 ) comprising cyclododecanone (CDON), cyclododecanol (CDOL) and the MB components from the side draw of the primary side draw column ( 7 ); 
 g) feeding the second mixture (ABC 2 ) into a secondary side draw column ( 8 ); 
 h) drawing off a second cyclododecanone-rich fraction (A 2 ) from the top of the secondary side draw column ( 8 ); 
 i) drawing off a second fraction (C 2 ) comprising cyclododecanol (CDOL) and the HB components from the bottom of the secondary side draw column ( 8 ); 
 j) drawing off a third mixture (ABC 3 ) comprising cyclododecanone (CDON), cyclododecanol (CDOL) and the MB components from the side draw of the secondary side draw column ( 8 ); 
 k) combining the first cyclododecanone-rich fraction (A 1 ) and the second cyclododecanone-rich fraction (A 1 ) to obtain the cyclododecanone-rich target fraction (A). 
 
     
     
       2. The process according to  claim 1 , wherein the second mixture (ABC 2 ) is drawn off in liquid form from the primary side draw column and introduced in liquid form into the secondary side draw column. 
     
     
       3. The process according to  claim 2 , wherein the second mixture (ABC 2 ) is drawn off at a separation plane of the primary side draw column at which the liquid concentration of the MB components in the primary side column is at a maximum, and in that the second mixture (ABC 2 ) is fed in at a separation plane of the secondary side draw column at which the MB component composition corresponds essentially to the composition of the liquid phase at the feed separation plane of the primary side draw column. 
     
     
       4. The process according to  claim 1 , further comprising feeding the first fraction (C 1 ) comprising cyclododecanol (CDOL) and the HB components and the second fraction (C 2 ) comprising cyclododecanol (CDOL) and the HB components in combination to a distillation stage which at least partly removes the high boilers. 
     
     
       5. The process according to  claim 1 , wherein both side draw columns are operated at a pressure below 1 bar absolute. 
     
     
       6. The process according to  claim 5 , wherein the reduced pressure in the side draw columns is generated by a common vacuum unit. 
     
     
       7. The process according to  claim 1 , wherein a composition of the dehydrogenation mixture (O) is:
 Low boilers (LB): 1 to 8% by weight; 
 Cyclododecanone (CDON): 60 to 90% by weight; 
 Medium boilers (MB): 0 to 1.5% by weight; 
 Cyclododecanol (CDOL): 10 to 40% by weight; 
 High boilers (HB): 0.1 to 2.5% by weight; 
 wherein a sum of the weight % values is 100%. 
 
     
     
       8. The process according to  claim 1 , wherein a content of cyclododecanone (CDON) in the cyclododecanone-rich target fraction (A) is at least 98% by weight. 
     
     
       9. The process according to  claim 1 , wherein the cyclododecanone-rich target fraction (A) is free of cyclododecanol (CDOL), high boilers (HB) and medium boilers (MB). 
     
     
       10. The process according to  claim 1 , wherein each of the fractions (C 1 , C 2 ) comprising cyclododecanol (CDOL) and the HB components is free of cyclododecanone (CDON). 
     
     
       11. The process according to  claim 1 , wherein the dehydrogenation mixture (O) is obtained by a process comprising:
 l) oxidation of cyclododecane (CDAN) with oxygen to obtain an oxidation mixture ( 2 ) comprising the LB components, cyclododecanone (CDON), the MB components, cyclododecanol (CDOL) and the HB components 
 m) distillatively removing a cyclododecanol-rich fraction (CBOL technical quality) (CDOL t.q.) from the oxidation mixture ( 2 ); 
 n) removing the high boilers from the CDOL t.q. to obtain a fraction (C) comprising cyclododecanol (CDOL) and high boilers (HB); and 
 o) dehydrogenating the cyclododecanol-rich fraction from which the high boilers are removed to obtain the dehydrogenation mixture (O). 
 
     
     
       12. The process according to  claim 11 , wherein the fractions (C 1 , C 2 ) comprising cyclododecanol (CDOL) and high boilers (HB) are recycled into distillation m). 
     
     
       13. The process according to  claim 1 , further comprising:
 oximating the cyclododecanone-rich fraction (A) to obtain an oxime of cyclododecanone; and 
 reacting the cyclododecane oxime with sulfuric acid to obtain laurolactam.